In order to support Leno you have to believe he deserved the show in the first place.
Amazingly, he has now stolen The Tonight Show from two Late Night hosts.
When Leno took over the Tonight Show originally his ratings were so bad NBC wanted to pull the plug and offered the job to Letterman, who refused.
Under Carson the Tonight Show was the place for comedians to get their start, including Leno himself. When Leno took over, no more comedians appeared on the show (he didn't like being upstaged). Conan was bringing back the stand-up acts.
It took years and years for Leno to build an audience. Conan only got 7 months.